Resin binders and process for preparing them

ABSTRACT

An unsaturated polyester suitable as a binder which comprises a reaction product of 
     (A) an acid component comprising one or a mixture of α,β-mono-olefinically unsaturated dicarboxylic acids or polycarboxylic acids free from polymerizable carbon-carbon multiple bonds or functional derivatives thereof, 
     (B) a polyhydric alcohol, 
     (C) a polycyclic compound containing a norbornane ring system and having one or more identical substituents selected from carboxyl, hydroxy and amino groups, and 
     (D) an acrylic compound which is capable of condensing with at least one of components (A) to (C) and a process of their preparation.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a Continuation of Copending Application Ser. No. 724,004, filedSept. 16, 1976 now abandoned.

The invention relates to radiation hardenable binders suitable forcoating systems, in particular solvent-free printing inks.

In general coating systems of this kind comprise a binder whichgenerally contains ethylenic carbon-carbon double bonds, a reactivediluent which is copolymerisable therewith, at least one sensitizer andusually, in the case of printing inks, a pigment.

Coating systems of this kind should desirably harden, i.e. cross-link,rapidly under the effect of high energy radiation, preferablyultra-violet light, and in the case of printing inks should form a hardbut flexible film with good adhesion, high gloss, good pigment wettingand thus a high colour intensity. Furthermore, the inks should becapable of being processed satisfactorily in printing machines,particularly offset machines, and should have an adequate storagestability.

The use of radiation hardenable ethylenically unsaturated resins incoating compositions, adhesives and printing inks is known. Under theeffect of high energy radiation, particularly when mixed withphotosensitizers, these resins polymerise. However, the standardcommercial products frequently are unsatisfactory with regard to theirpigment wetting and storage stability, in that they do not wet pigmentssufficiently or they thicken when stored therewith. Moreover, the inksproduced therefrom sometimes have poor printing properties. Thus, forexample, acrylated epoxy resins tend to "pull", i.e. the printing inksticks to the rollers or to the rollers and paper, and this cansometimes result in tearing of the paper.

Hardenable synthetic resins in admixture with acrylamide compounds oftenhave the disadvantage that they have too high a viscosity. Theytherefore have to be mixed with a relatively large amount of reactivediluent as a result of which the drying speed suffers. Frequently,crystallisation and phase separation occurs in the printing ink makingprocessing more difficult or impossible.

Moreover, systems based on polyacrylates obtained by reacting polyhydricalcohols with dicarboxylic acids and then reacting the product withacrylic or methacrylic acid have been proposed. These systems generallyhave more satisfactory processing characteristics and have a high glossbut they do tend to have certain disadvantages, namely their dryingtimes are too long and they thus do not meet the requirements of modernpractice.

The binders for radiation hardenable polyester systems describedhitherto generally have at least one easily polymerisable carbon-carbondouble bond, i.e. they are α,β-olefinically unsaturated. However,unsaturated polyester resin systems have also been proposed in which thedouble bond is in an isocyclic ring. Typical resins of this kind have alinear construction and contain substituted or unsubstituted unsaturatedbicyclo-(2,2,1)-heptenyl-(2) groups either in the polymer chain or inside chains. However, when subjected to radiation, it is found thatthese resins harden unsatisfactorily.

Further unsaturated polyesters, hardenable by free radicalpolymerisation mechanisms, are known which are prepared from polyhydricalcohols and α,β-olefinically unsaturated polycarboxylic acids,optionally a proportion of these unsaturated acids being replaced bysaturated aliphatic and/or aromatic polycarboxylic acids, and whichadditionally comprise bi- or tricyclic dihydroxy compounds containing anendomethylene group, for example, dimethylol dicyclopentadiene anddicyclodicarboxylic acids which contain an endomethylene group, e.g.hexachloroendomethylene tetrahydrophthalic acid. Unsaturated polyestersare also known wherein the diol rather than the acid components arepartially replaced by di- or tricyclic diols, for example dimethylolbicyclo-(2,2,1)-heptane and dimethylol tricyclo-(5,2,1,0²,6)-decane. Thepresence in the unsaturated polyester of these compounds containing di-or tricyclic endomethylene groups brings about an increase in thehardening speed and thus a reduction in the time taken to reach anon-tacky state.

Instead of the unsaturated di- or tricyclic components, it has also beenproposed to use polyesters obtained by reacting a saturateddicyclopentadiene derivative, e.g.3(4),8(9)-dihydroxymethyltricyclo-(5,2,1,0²,6)-decane, with unsaturateddicarboxylic acids. These polyesters may also be processed, like styrenecopolymers, to form solvent-free rapid drying enamels, but cannot besubjected to UV hardening.

Resins hardenable by the effect of high energy radication have also beendescribed which consist of a mixture (A) of an unsaturated polyester,(B) a norbornene carboxylic acid derivative and (C) optionally acopolymerisable vinyl monomer. Component (B) may also be esterified viathe acid group with an alcohol containing a tricycloalkylene group e.g.a tricyclo-(5,2,1,0²,6)-dec-3-ene group. This mixture polymerises duringthe hardening process, whilst the copolymerisable monomer isincorporated into the resin.

Although some of the aforementioned binders have found practicalapplication, there is still a search for products having improvedproperties. Thus, it is desired to improve the processability and shelflife of pigment-containing printing inks and moreover to increase thegloss of the print.

According to the present invention there is provided an unsaturatedpolyester suitable as a binder which comprises a reaction product of

(A) an acid component comprising one or a mixture ofα,β-mono-olefinically unsaturated dicarboxylic acids or polycarboxylicacids free from polymerisable carbon-carbon multiple bonds or functionalderivatives thereof,

(B) a polyhydric alcohol,

(C) a polycyclic compound containing a norbornane ring system and havingone or more identical substituents selected from carboxyl, hydroxy andamino groups, and

(D) an acrylic compound which is capable of condensing with at least oneof components (A) to (C).

The new binders according to the invention are generally hardenable withUV radiation and have improved properties over the radiation hardenablebinders used heretofore. They may be prepared by a process whichcomprises reacting in a first stage components (A), (B), and (C) toproduce a polyester product which is subsequently reacted in a secondstage with (D) an acrylic compound which is co-condensable therewith.

The polyester resin intermediate product contains hydroxy groups asreactive groups. In the second stage this polyester resin, which may ormay not be unsaturated, undergoes an esterification ortransesterification reaction between the hydroxy groups and the acryliccompound.

Polycarboxylic acids free from aliphatic carbon carbon multiple bondswhich may be used as component (A) are, for example, saturated aliphaticand cycloaliphatic polycarboxylic acids with 4 to 13 carbon atoms, e.g.succinic acid, dimethylsuccinic acid, adipic acid, azelaic acid, sebacicacid, brassydic acid and hexahydrophthalic acid, and aromaticpolycarboxylic acids with 8 or 9 carbon atoms, e.g. the various phthalicacids and trimellitic acid. Mono-olefinically unsaturated dicarboxylicacids which may be used are, for example, aliphatic unsaturated acidswith 4 or 5 carbon atoms e.g. maleic, fumaric, itaconic, mesaconic,citraconic and chloromaleic acid.

If desired the polyesters according to the invention can be modified byincorporation of further acid components, in particular benzophenoneswhich are substituted by at least one carboxyl group and then act asinternal sensitisers, fatty oils and/or unsaturated fatty acids, thosehaving a conjugated diene system, e.g. 9,11-ricinoleic acid and/or10,12-linoleic acid, being preferred, and saturated fatty acids whichact as internal plasticisers. The proportion of modifying acidcomponents should generally be not more than 30%, preferably up to 20%and particularly up to 10%, based on the total weight of acid component(A).

Preferred polyhydric alcohols which may be used as component (B) are di-to tetrafunctional, saturated or olefinically unsaturated alcohols withup to 15 carbon atoms, e.g. ethanediol, the various propane, butane-,pentane-and hexane-diols, dimethylolcyclohexane,bis-(4-hydroxycyclohexyl)-methane and -propane, Δ²,3 -butenediol-1,4,glycerol, trimethylolethane and -propane and pentaerythritol. Mixturesof these polyhydric alcohols may also be used. Alcohols containing onlyprimary hydroxyl groups are preferred, particularly trimethylolpropaneand ethanediol.

Acrylic compounds which may be used as component (D) are those which canreact with the functional groups of the polyester intermediate productof components (A) to (C). Preferred are acrylic and methacrylic acidsand their functional derivatives, for example their anhydrides andchlorides. Condensation of the acrylic compound may be effected viatransesterification of the polyester intermediates containing hydroxygroups with suitable esters of acrylic and methacrylic acid, e.g. alkylesters. This however, results in the alcohol group being split off andis thus less preferred. The proportion of acrylic compounds incorporatedinto the binder is generally from 10 to 50%, preferably more than 20% byweight, based on the polyester resin product of the second step.

Polycyclic compounds which may be used as component (C) of the binderare endocyclic compounds substituted with carboxyl, hydroxy and aminogroups, e.g. tricyclo-(5,2,1,0²,6)-decan-3(4)-carboxylic acid ##STR1##

However, polycyclic compounds having a 5-membered ring containing acarbon-carbon double bond fused to the norbornane ring system, forexample ##STR2## are also suitable for the preparation of the polyesterbinders according to the invention.

Mixtures of these polycyclic compounds may also be used.

Generally, however, the polycyclic compounds are obtained as isomericmixtures by the technical process of preparation and are applied in thisform to prepare the claimed polyesters.

The content of polycyclic compounds incorporated into the binder isgenerally at least 0.5%, preferably from 3 to 30% by weight, based onthe modified polyester resin obtained in the second step.

As discussed hereinbefore the polyester intermediate product containshydroxy groups, which appropriately have hydroxy numbers (determinedaccording to DlN standard 53240) in the range from 100 to 1000,preferably from 200 to 800, most preferably from 400 to 600. In thereaction with the acrylic compounds it is preferred that at least 2%,advantageously from 10 to 35% of the hydroxy groups do not react. Theresin is then easier to prepare since it does not have such a greattendency to cross-linking reactions and thus to undesirable prematuregelatinisation and, moreover, has better pigment wetting qualities.

The viscosity of the finished polyester resin binder is generally in therange from 100 to 800 P (20° C., rotoviscosimeter) although it is alsopossible to use polyesters with higher viscosities, for example thosewith viscosities of up to 1500 P. Generally, however, a low viscosity isparticularly advantageous for the further processing of the polyester.

The polyester resins are appropriately prepared in the first step underthe conditions conventionally used for polycondensation resins, e.g. bycondensation in a melt, by esterification with azeotropic distillationof the water formed during the reaction, or by transesterification.Towards the end of the esterification, which generally takes place at areaction temperature in the range from 160° to 250° C., it is advisableto work under reduced pressure, at least for a short time, in order todistil off water, any unreacted volatile starting materials and lowmolecular weight reaction products. Subsequently, at least one acryliccompound is added to this resin and further esterification which may becomplete or partial, of the free hydroxy groups takes place under theconditions described further hereinafter.

Whereas, in the first step, no polycondensation catalysts are generallyused, in the second step it is convenient to work in the presence of anesterification, for example sulphuric acid, hydrochloric acid,benzenesulphonic acid, p-toluenesulphonic acid and methanesulphonicacid. The catalysts are generally added in quantities of from 0.1 to 5%,preferably 0.5 to 2% by weight, based on the total quantity of thereaction components.

In the second process step, it is also advantageous to work in thepresence of a entrainer, for example cyclohexane, benzene, toluene,xylene, petroleum fractions with an appropriate boiling range, e.g.n-hexane, trichloroethylene and isopropyl ether. The second stage ispreferably effected at a reaction temperature in the range from 70° to120° C., depending on the type and quantity of retarder used. It issometimes advisable to work under reduced pressure. The course of thereaction can be monitored by determining the quantity of water formedand the reaction can be regarded as complete when more than 95% of thetheoretical quantity of water has been separated off.

In order to avoid polymerisation reactions occurring in the second stepin which unsaturated compounds are present a polymerisation inhibitor isgenerally added, conveniently in a quantity of 0.1 to 5%, preferably 0.5to 2% by weight, based on the total weight of reaction components.Typical polymerisation inhibitors are, for example, quinone derivativese.g. hydroquinone and p-benzoquinone, substituted phenols e.g.p-tert.butylphenol, p.tert.butyl-pyrocatechol, 2,6-di-tert.butylcresoland p-methoxyphenol, amines e.g. diphenylamine, sulphur and sulphurcompounds e.g. thiosemicarbazide and phenothiazine.

After the reaction, any azeotropic dehydrating agent used can bedistilled off under reduced pressure preferably in a thin-layer orrotary evaporator.

The binders according to the invention may be formulated into coatingsystems by admixture with one or more reactive diluents, sensitisersand/or pigments. Such compositions find particular application asprinting inks, coating materials, adhesives and, if fillers are alsoadded, as trowelling compounds. The binder imparts to the compositiongood storage properties and a high hardening speed when irradiated withUV light. Printing ink drying speeds of more than 400 m/min, can forexample, be obtained, whilst the print produced therewith has high glossand colour intensity.

Although UV light is already sufficient to obtain a high hardeningspeed, irraditation of course may also be effected by means of a moreenergetic radiation source e.g. electron beam.

The viscosity of the composition can be adjusted as required for theparticular intended use by adding one or more reactive diluents forexample in amounts of to up to 60% by weight, based on the totalcomposition. Acrylic and methacrylic acid esters of mono- and/orpolyhydric alcohols, e.g. 2-ethylhexanol, ethane diol, the variouspropane- and butanediols, trimethylolpropane and pentaerythritol, areadvantageously used as reactive diluents, alone or in admixture.

A sensitiser may be added to the composition to increase its hardeningspeed. Typical sensitisers are, for example, ketones e.g. benzoin,benzophenone and Michler's ketone, benzoic acid esters, ethers, ketals,chlorinated aromatic compounds, and anthraquinone derivatives,combinations of benzophenone and Michler's ketone, e.g. in a 1:1 ratio,being preferred. The quantity of sensitisers is generally 2 to 20,preferably 3 to 10% by weight, based on the total composition. Theaddition of sensitisers can be omitted wholly or partially if aninternal sensitiser has already been incorporated into the polyester asdescribed hereinbefore. As already mentioned, benzophenones substitutedwith carboxyl groups are preferred for chemical incorporation.

For the preparation of printing inks and pigmented enamels from 5 to40%, preferably 8 to 20% by weight, of pigment based on the totalcomposition, is appropriately added. Suitable pigments are the knowncompounds conventionally used in the dye and printing ink industry, forexample organic pigments, e.g. pigment and dyes of the azo series,complex pigments and dyes, anthraquinone dyes and quinacridone pigments,carbon black and inorganic pigments e.g. titanium dioxide, iron oxideand cadmium sulphide selenide. The pigments may be incorporated usingconventional apparatus used in the dye and printing ink industries, e.g.with a triple roller mill.

The binders according to the invention may also be combined with otherresin binders in order to obtain certain special properties for examplein amounts of up to 60% by weight, preferably 3 to 20% by weight, basedon the total composition. Resins with which the binders according to theinvention may be combined include, for example, acrylated epoxy resins,unsaturated polyesters, acrylamide containing systems, alkyd resins,cyclorubber, hydrocarbon resins based, for example, on cyclo- ordicyclopentadiene, colophony, acrylate and/or maleate resins,phenol-modified colophony resins provided that they are high-meltingtypes compatible with aliphatics, and phenolic resins. Maleate resins,for example, may be added to printing inks to improve the processingcharacteristics in offset machines, without negatively affecting thedrying speed.

The following Examples serve to illustrate the polyester bindersaccording to the invention. The preparation of the binders and ofprinting inks containing them was carried out as follows:

PREPARATION OF BINDERS Step 1

The carboxylic acid and the alcohol components are intimately mixed withthe polycyclic compound and any other additive in a flask fitted with astirrer, thermometer and water separator, and the mixture is kept at atemperature in the range from 160° to 250° C., with stirring, until thetheoretical quantity of water has separated off.

Step 2

The polyester resin formed in the step 1 is dissolved in an azeotropicdehydrating agent and the acrylic compound, an inhibitor and catalystare added. The mixture is heated to 70°-120° C. and the azeotropicdehydrating agent is then distilled off, if necessary under reducedpressure. After removal of water by azeotropic distillation, thedehydrating agent is recycled into the reaction mixture. The catalyst isthen washed out of the resin solution in known manner, after whichsolvent is distilled off under reduced pressure at 50° to 70° C.

PREPARATION OF PRINTING INKS

The viscosity of the resin binder is first adjusted to about 200 P withtrimethylolpropane triacrylate and 15% of pigment and 8% by weight of amixture of benzophenone and Michler's ketone as sensitiser are thenadded. The increase in viscosity produced by the incorporation of theseadditives is counteracted by addition of a further portiontrimethylolpropane triacrylate until the viscosity is 400 P.

In the following Examples, T indicates parts by weight.

EXAMPLE 1

348 T of trimethylolpropane are condensed with 292 T of adipic acid and36 T of a compound of formula ##STR3## at 200° C., under theaforespecified conditions. 75 T of water are separated off. 100 T of theresin obtained (OH number 330) are dissolved in 150 T of toluene and36.7 of acrylic acid, 0.75 T of 2,6-di-tert.butylcresol and 1 T of conc.sulphuric acid are then added. The mixture is reacted at 95° C. underslightly reduced pressure. After separation of the water which formssolvent is distilled off and a yellowish resin with a viscosity of 647 P(determined at 20° C. with the rotoviscosimeter made by Messrs GebruderHaake) is obtained.

COMPARISON EXAMPLE 1

Example 1 is repeated, but without adding the compound formula I. The OHnumber of the polyester intermediate produced is 350. A colourless resinis obtained with a viscosity of 250 P.

COMPARISON EXAMPLE 2

Example 1 is repeated but instead of the compound of formula I anequimolar quantity of benzoic acid is added. The OH number of thepolyester intermediate produced is 340. A light coloured resin isobtained with a viscosity of 470 P.

COMPARISON EXAMPLE 3

Example 1 is repeated but instead of the compound of formula I anequimolar quantity of acetic acid is added. The OH number of thepolyester intermediate produced is 340.200 T of toluene are added instep 2 of the process. A colourless resin is obtained with viscosity of157 P.

EXAMPLE 2

450 T of trimethylolpropane are condensed with 263 T of adipic acid and54 T of a compound of formula I at 200° C. 70 T of water are separatedoff. 100 g of the resin produced (OH number 490) are dissolved in 150 Ttoluene and 43.8 T of acrylic acid, and 0.75 T of2,6-di-tert.butylcresol and 1 T of concentrated sulphuric acid areadded. The mixture is reacted as in Example 1. After azeotropic removalof the water formed, the solvent is distilled off under reducedpressure, and a slightly yellowish resin with a viscosity of 753 P isobtained.

EXAMPLE 3

450 T of trimethylolpropane, 263 T of adipic acid and 58 T of a compoundof formula ##STR4## are condensed at 200° C. 65 T of water are separatedoff. 100 T of the resin produced (OH number 560) are dissolved in 150 Tof toluene and 43.8 T of acrylic acid and, after the addition of 1 T of2,6-di-tert,butylcresol and 1.5 T of concentrated sulphuric acid, themixture is reacted as in Example 1. When no more water separates, thesolvent is distilled off and a slightly yellowish resin with a viscosityof 725 P is obtained.

PRINTING TESTS

In order to determine the drying speed of the individual printing inks,sample prints were produced on white paper with an average applicationof 1.5 g/m² of printing ink and irradiating with a mercury vapourpressure lamp at 80 watts/cm at various running speeds. The drying speedis given as the radiation time required to dry i.e. cross-link,irradiated print to such an extent that when a sheet of white paper isapplied, under a contact pressure of 130 kp/cm², there is no transfer ofink on to the white paper (the so called "off setting test", carried outusing a print testing apparatus made by Messrs. Durner, Peissenberg,Federal Republic of Germany). The gloss was assessed visually. Theresults of the printing tests are given in the Table which follows:

                                      TABLE                                       __________________________________________________________________________    Binder preprared in                                                                     Pigment    Drying speed                                             Example No.                                                                             C.I. number                                                                              ca. m/min.                                                                             Gloss                                           __________________________________________________________________________    1         Pigment Yellow                                                                        126                                                                              180      excellent                                                 Pigm. Blue                                                                            15 270      very good                                       comparison 1                                                                            Pigm. Yellow                                                                          126                                                                              40       good                                                      Pigm. Blue                                                                            15 40       good                                            comparison 2                                                                            Pigm. Yellow                                                                          126                                                                              80       satisfactory                                              Pigm. Blue                                                                            15 80       moderate                                        comparison 3                                                                            Pigm. Yellow                                                                          126                                                                              20       not very good                                             Pigm. Blue                                                                            15 20       the print bronzes                               2         Pigm. Yellow                                                                          126                                                                              240      good                                                      Pigm. Blue                                                                            15 300      good                                            3         Pigm. Yellow                                                                          126                                                                              190      very good                                                 Pigm. Blue                                                                            15 210      good                                            __________________________________________________________________________

The printing inks containing the binder prepared in Example 1 have aparticularly high gloss and good drying properties and those containingthe binder prepared in Example 2 have a good gloss and very good dryingproperties. In contrast, the inks containing the binders prepared in thecomparison Examples have less good drying properties and some have avery inferior gloss. It makes no difference whether the binder isunmodified (comparison Example 1) or modified with an aromatic(comparison Example 2) or aliphatic (comparison Example 3) acid. Theinks prepared with the binder of Example 3 have a high gloss and gooddrying properties The binders according to the invention aredistinguished by high storage stability, i.e. in a six-month period theyshow no gel formation, no concentration and no change in viscosity.Similarly the storage stability of the mixtures prepared with thebinders is also excellent.

It is not intended that the examples given herein should be construed tolimit the invention thereto, but rather they are submitted to illustratesome of the specific embodiments of the invention. Resort may be had tovarious modifications and variations of the present invention withoutdeparting from the spirit of the discovery or the scope of the appendedclaims.

We claim:
 1. An unsaturated polyester which comprises a reaction productof, in a first step(A) at least one compound selected from the groupconsisting of α,β-mono-olefinically unsaturated dicarboxylic acids,polycarboxylic acids free from polymerisable carbon-carbon multiplebonds and functional derivatives thereof (B) at least one polyhydricalcohol, and (C) at least one tricyclo-(5,2,1,0²,6)-decane derivative inan amount of 0.5 to 30% by weight based on the polyester resin, saidtricyclo-(5,2,1,0²,6)-decane derivative being substituted by hydroxyl,carboxyl or amino groups, to thereby form an intermediate polyesterhaving reactive hydroxy groups, and (D) at least one acrylic compoundwhich is added in a separate second stage and which is reacted with thepolyester intermediate products of components (A) to (C) and saidacrylic compound is selected from the group consisting of acrylic acidand methacrylic acid wherein the reaction between the intermediatepolyester and the acrylic compound is effected through the carboxylicgroup of the acrylic compound.
 2. A polyester as claimed in claim 1wherein the polyhydric alcohol (B) has only primary alcohol groups.
 3. Apolyester as claimed in claim 1 wherein compound (C) contains acarbon-carbon double bond in a 5-membered ring fused to thetricyclo-(5,2,1,0²,6)-decane derivative.
 4. A polyester as claimed inclaims 1 wherein the acrylic compound (D) is selected from the groupconsisting of acrylic and methacrylic acid and is present in an amountof from 10 to 50% by weight, referred to the polyester.
 5. A process forthe preparation of a binder as claimed in claim 1 based on anunsaturated polyester wherein in a first reaction step(A) at least onecompound selected from the groups consisting of α,β,mono-olefinicallyunsaturated dicarboxylic acids, polycarboxylic acids free frompolymerisable carbon-carbon multiple bonds, functional derivativesthereof (B) at least one polyhydric alcohol and (C) at least onetricyclo-(5,2,1,0²,6)-decane derivative in an amount of 0.5 to 30% basedon the polyester resin, said tricyclo-(5,2,1,0²,6)-decane derivativebeing substituted by hydroxyl, carboxyl or amino groups, are reactedtogether to thereby form an intermediate polyester having reactivehydroxy groups followed by a second reaction step with (D) at least oneacrylic compound which is reacted therewith and said acrylic compound isselected from the group consisting of acrylic acid and methacrylic acidwherein the reaction between the intermediate polyester and the acryliccompound is effected through the carboxylic group of the acryliccompound.
 6. A process as claimed in claim 5 wherein the first step iseffected at a temperature in the range from 160° to 250° C. and thesecond step in the range from 70° to 120° C.
 7. A process as claimed inclaim 5 wherein the second step is performed under reduced pressure inthe presence of an entrainer, an esterification catalyst in an amountfrom 0.1% to 5% and a polymerisation inhibitor, in an amount of from 0.1to 5%, both referred to the weight of reaction component (A) to (D). 8.A process as claimed in claim 5 wherein a polyester product of the firstreaction step having a hydroxy number in the range from 100 to 1000 ispartially esterified in the second step with component (D) to yield aproduct in which at least 2% of the hydroxy groups of the polyesterremain unreacted.
 9. A coating composition which comprises as a binderan unsaturated polyester as claimed in claim 1 in admixture with atleast one further ingredient selected from the group consisting ofreactive diluents, sensitisers, pigments and further synthetic resins.10. A composition as claimed in claim 9 as printing ink.
 11. A coatingcomposition which comprises as a binder an unsaturated polyester asclaimed in claim
 1. 12. A coating composition which comprises as abinder an unsaturated polyester as claimed in claim 11 in admixture withpigments.
 13. An unsaturated polyester which comprises a reactionproduct of, in a first step,(A) at least one polycarboxylic acid freefrom polymerisable carbon-carbon multiple bonds, (B) at least onepolyhydric alcohol, and (C) at least one tricyclo-(5,2,1,0²,6)-decanederivative in an amount of 0.5 to 30% by weight based on the polyesterresin, said tricyclo-(5,2,1,0²,6)-decane derivative being substituted byhydroxyl, carboxyl, or amino groups, to thereby form an intermediatepolyester having reactive hydroxy groups,and (D) at least one acryliccompound selected from the group consisting of acrylic acid andmethacrylic acid which is added in a separate stage and which is reactedwith the polyester intermediate products of components (A) to (C)through the carboxylic group of the acrylic compound.
 14. A process forthe preparation of a binder as claimed in claim 13 based on anunsaturated polyester wherein in a first reaction step(A) at least onepolycarboxylic acid free from polymerisable carbon-carbon multiplebonds, (B) at least one polyhydric alcohol, and (C) at least onetricyclo-(5,2,1,0²,6)-decane derivative in an amount of 0.5 to 30% byweight based on the polyester resin and having at least one carboxylicsubstituent, are reacted together to thereby form an intermediatepolyester having reactive hydroxy groups followed by a second step with(D) at least one acrylic compounds selected from the group consisting ofacrylic acid and methacrylic acid which is reacted therewith through thecarboxylic group of the acrylic compound.
 15. A polyester as claimed inclaim 1 wherein component (A) is modified by at least one componentselected from the group consisting of benzophenones substituted by atleast one carboxyl group, fatty oils, saturated fatty acids andunsaturated fatty acids up to 30% by weight, referred to the acidcomponent (A).